article description

Show More Hide

Quinones are involved in many biological pathways.It is essential to understand their basic chemical properties.Substitution process is often involved in the reactions of quinones.Here we study the reactions of 2-bromo-3-methoxy-1,4-naphthoquinone with secondary alklylamines.Various alkylamines were chosen to react with 2-bromo-3-methoxy-1,4-naphthoquinone.Reactions of 2-methoxy-1,4-naphthoquinone with secondary alkylamines were also studied in order to understand the role of bromine atom.Since a methoxy group is not considered a good leaving group in nucleophilic substitution,it was expected that an alkylamine would replace the bromine atom.In reality, however,an alkylamine was found to replace the mothoxy group in 2-bromo-3-methoxy-1,4-naphthoquinone.By comparing the stability of the product of a secondary alkylamine with 2-methoxy-1,4-naphthoquionone,we found that the bromine would make the substitution product more readily decomposing.The product in the reaction of 2-bromo-3-methoxy-1,4-naphthoquinone with N-methylethylamine,for example,is 2-bromo-3-N-methylethylamino-1,4-naphthoquinone. This product was found to decompose through dealkylation,where one of the alkyl groups was lost. The major decomposition product was identified as 2-bromo-3-methylamino-1,4-naphthoquinone by losing ethyl group.On the other hand, no decomposition was detected in reaction product of 3-methoxy-1,4-naphthoquinone with N-methylethylamine,that is,2-N-methylethylamino-1,4-naphthoquinone.Our observation suggests the bromine plays a critical role in the stability of the product.